Question

1) If n=19, ¯xx¯(x-bar)=33, and s=18, construct a confidence interval at a 80% confidence level. Assume the data came from a normally distributed population.

Give your answers to one decimal place.

< μμ <

2) You measure 48 backpacks' weights, and find they have a mean weight of 44 ounces. Assume the population standard deviation is 2.8 ounces. Based on this, construct a 95% confidence interval for the true population mean backpack weight.

Give your answers as decimals, to two places

±±  ounces

3) You measure 33 textbooks' weights, and find they have a mean weight of 45 ounces. Assume the population standard deviation is 8.7 ounces. Based on this, construct a 95% confidence interval for the true population mean textbook weight.

Give your answers as decimals, to two places

< μμ <

Answer 1

Given :

n =19, = 33, and s = 18, = 1-0.80 = 0.20

Degree of freedom = df = 19-1 = 18

At 80% significance level, the critical value of t is

42.03 < < 47.97